Lens fed antenna array system

ABSTRACT

A circular phased array system is described which utilizes a lens feed to simplify the problem of commutating the RF distribution system through 360* of steering of the antenna beam. The lens feed consists of a circular parallel-plate radial transmission line with a central set of probes and a ring of peripheral probes. The peripheral probes are coupled via switches to an array of radiating elements arranged in a circle. The central set of probes can be energized and phased to produce electromagnetic energy with an amplitude distribution within the parallel-plate line in any given direction. By selective settings of phase and amplitude of the energy coupled to the central set of probes to achieve the proper energy distribution to the peripheral probes and by operating the switches to determine which radiating elements are coupled to the peripheral probes, a desired directive antenna pattern with low side lobes is provided.

tates Bogner et al.

atet 1 LENS FED ANTENNA ARRAY SYSTEM [75] Inventors: Bruce FredricBogner, Mt. Holly;

David Francis Bowman, Moorestown, both of NJ.

[52] US. Cl 343/754, 343/876, 343/854 [51] Int. Cl. HOlq 19/06 [58]Field of Search 343/754, 755, 876, 854

[56] References Cited UNITED STATES PATENTS 3,568,207 3/l97l Boyns ctal. 343/854 Primary ExaminerEli Lieberman Attorney, Agent, orFirm-Edward J. Norton; Robert L. Troike 5 7] ABSTRACT A circular phasedarray system is described which utilizes a lens feed to simplify theproblem of commutating the RF distribution system through 360 ofsteering of the antenna beam. The lens feed consists of a circularparallel-plate radial transmission line with a central set of probes anda ring of peripheral probes. The peripheral probes are coupled viaswitches to an array of radiating elements arranged in a circle. Thecentral set of probes can be energized and phased to produceelectromagnetic energy with an amplitude distribution within theparallel-plate line in any given direction. By selective settings ofphase and amplitude of the energy coupled to the central set of probesto achieve the proper energy distribution to the peripheral probes andby operating the switches to determine which radiating elements arecoupled to the peripheral probes, a desired directive antenna patternwith low side lobes is provided.

10 Claims, 14 Drawing Figures PATENIED HL 3.827, 055

sum 1 or 6 NORTH 37 $40 POWER 29 msmmumm NETWRK Hg 3 PATENTEB JUL 301974 SHEET 2 BF 6 PAIENTED JUL3 0 I974 sum 5 or 6 PATENTEU JUL 3 01974SHEEF 5 UP 6 1 LENS FED ANTENNA ARRAY SYSTEM BACKGROUND OF THE INVENTIONThis invention relates to electronic beam steering antennas and,particularly, to a circular array of many antenna elements with meansfor beam steering through 360 in fine increments or continuously.

The five most common approaches to provide beam steering through 360with such an array of antenna elements are briefly described inconnection with a typical 192-element circular array, for example. Atotal of 48 active radiating elements are normally utilized to achieve adirectional beam. A first approach is a system that uses asector-ordering matrix to commutate the amplitude distribution and a setof phase shifters to fine-steer the beam. This first system for thisapplication includes a 1:48 power distribution network, a total of 484-bit phase shifters, a 48 X 48 switch matrix with 144 transfer switchesand a sector selection network. Beam steering has 11 fine steering phaseshifter gradients for the 48 phase shifters and 48 sector orderingcommands for the 144 switches. This system requires many diodes for thephase shifters and for transfer switching. High isolation per switch 40db) is also a requirement. For a more detailed description of this typeof system see An Electronically-Scanned Cylindrical Array Based on aSwitching-and-Phasing Technique by Richard J. Giannini, in the symposiumrecord of the December, 1969 IEEE G-AP (Antennas and Propagation Group)International Symposium, Austin, Tex.

A second approach is to employ a N X N Butler beam forming matrix toexcite an array of N elements or for the 192 element array a 192 X 192matrix. This network must employ N or 192 phase shifters for beamcommutation. A proposed diode count for such a system would be about1,536. A more detailed description of this arrangement may be had withreference to a paper entitled A Matrix Fed Circular Array for ContinuousScanning, by B. Sheleg, in the symposium record of the September, 1968IEEE G-AP (Antennas and Propagation Group), International Symposium.

A third approach referred to as the sector beam forming technique may beprovided for beam steering using a 48 X 48 Butler beam forming matrixwhich is used in conjunction with 48 phase shifters to index theamplitude and phase of a fixed feed network along the parts of acircular array, and a sectorselection network. A more detaileddescription of this may be had with reference to the article AnElectronically Scanned Cylindrical Array Switched in Aximuth andFrequency Scanned in Elevation," by B. Sheleg and B. D. Wright, inProceedings of the Conformal Array Antenna Conference, NELC, San Diego,Calif, January, 1970. This 48 X 48 Butler matrix has many disadvantages.Although the amplitude and phase distribution can be commutatedtogether, any phase error or circuit error affects both parameters. Inthe example, critical cancellations through six layers of directionalcouplers and five layers of fixed phase shifters are required to producethe output amplitude and phase distributions. All beams generated withina sector are unique, resulting in for example 500 separate phase rampsrequired for 500 beam positions per quadrant. This system has relativelylarge insertion losses because the signal must travel in the aboveexample through six couplers, five fixed phase shifters, longequalization lines, and through several crossover networks. For afurther discussion of the diadvantages of the sector beamformingtechnique, see the article entitled Effects of Random Errors on thePerformance of a Linear Butler Array, by M. J. Kiss, in IRE Transactions(Antennas and Propagation Group), November, 1962.

A fourth technique referred to generally as the vector-transfertechnique, for the above example, uses forty-eight (48) 4-bit phaseshifters, a 1:48 power divider, forty-eight (48) 4-bit attenuators andforty-eight (48) single pole four throw switches (SP4T) in a sectorselection network. This technique requires generally more diodes and hasconsiderably higher loss than the other approaches. For a more completedescription of this technique, see the article, Step-Scanned Circular-Array Antenna, by J. E. Boyns, C. W. Gorham, A. D. Munger, J. H.Provencher, J. Reindel and B. I. Small in- Proceedings of the ConformalArray Antenna Conference, NELC, San Diego, Calif, January, 1970.

A fifth possible technique for a ring array is the R-2R lens techniqueas described in the article, A Broadband Optical Feed for CircularArrays, by J. M. Devan, J. E. Boyns and A. D. Munger in the Proceedingof the Conformal Array Antenna Conference, NELC, San Diego, Calif,January, 1970. This system requires that the angle of the feed system ofa parallel plate lens by exactly twice that of the array. This wouldrequire a large diameter (or heavily loaded) lens. Moreover, it wouldhave a very large switching matrix.

A new antenna array system is described herein which includes a parallelplate lens feed assembly. The basic array system including the parallelplate lens feed assembly is the subject of application Ser. No. 353,421filed on the even date herewith. The basic system is exemplified by thearrangements shown in FIGS. 1 thru 3. This arrangement may require manyinner probes to achieve the required highly directional pattern withinthe lens feed assembly. It is also desirable to further reduce thepossibility of side and back lobes.

SUMMARY OF THE INVENTION Briefly, a phased array antenna system isdescribed which includes a parallel plate lens feed assembly with afirst plurality of probes arranged in a ring at the periphery of theplates and a second plurality of central probes. A plurality ofradiating elements is arranged in a ring-like pattern with N times asmany elements as there are probes in the first plurality of probes. Aplurality of N-way switches are provided with a different N-way switchcoupled to each probe of said first plurality of probes. Each of theseN-way switches are coupled to N radiating elements which elements aredistributed uniformly about the array. Control of the direction of theradiated beam is had by controlling the power distribution and phase ofthe signals to the central probes to achieve an energy distribution tothe peripheral probes and by controlling the position of the N-wayswitches to control which antenna elements are coupled to the peripheralprobes.

DETAILED DESCRIPTION A more detailed description follows in conjunctionwith the following drawings in which:

FIG. 1 is a sketch of a 360 electronically scanned phased arrayaccording to one embodiment of the present invention.

FIG. 2 is a sketch of the feed system in FIG. 1 showing a cross-section'of the parallel plate radial transmission line lens feed assembly ofFIG.- 1 taken along line 2-2 with the power distribution network coupledthereto.

FIG. 3 is an illustrative sketch of the fine steering portion of thearray shown in FIG. 1.

FIG. 4 is a sketch of an antenna feed system in accordance with a secondembodiment of the present invention.

FIG. 5 is a plan view of the radial waveguide lens feed assemblyaccording to the second embodiment of the present invention.

FIG. 6 is a cross-sectional view of the radial parallel plate feedassembly of FIG. 5 taken along lines 6-6.

FIG. 7 is a partial cross sectional view of the parallel plate line feedassembly illustrating the probes with the center conductor having aconical taper in accordance with one embodiment of the presentinvention.

FIG. 8 is a sketch illustrating the coarse steering arrangementaccording to the second embodiment of the present invention.

FIG. 9 is a sketch of azimuth patterns illustrating how the rotatablecardioid pattern is derived.

FIG. 10 is a sketch of an azimuth pattern of a rotating phaseomnidirectional pattern that is phase shifted an extra +30.

FIG. 11 is a sketch of an azimuth pattern of a rotating phaseomnidirectional pattern that is phase shifted a (minus) 30.

FIG. 12 illustrates the power distribution feed network of the secondembodiment of the present inventron.

FIG. 13 is a sketch of an azimuth pattern of two orthogonal figure-eightpatterns.

FIG. 14 is a plan view of a radial waveguide lens feed assemblyaccording to a third embodiment of the present invention.

Referring to FIG. 1, there is illustrated a 48-element phased arrayantenna system 10 with 360 scan. The antenna array system 10 includes acylindrical array support structure 15, a lens feed assembly 11, 48radiating elements 13 and 48 feed lines 17. The lens feed assembly 11 islocated coaxially within the cylindrical support structure 15 for theradiating elements 13. The 48 peripherally mounted radiating elements 13are equally spaced about the array structure 15 and they extend inradial fashion from the center of the cylindrical structure 15. The 48feed lines 17 are coupled between 48 outer probes 27 associated with theparallelplate transmission line lens feed assembly 11 and the radiatingelements 13. The radial parallel plate transmission line lens feedassembly 11, as shown in FIGS. 1 and 2, includes a pair of paralleloverlapping conductive circular plates or disks 19 and 21 with adielectric medium 23 therebetween so as to form a transmission line. Thecircular plates or disks 19 and 21 are of the same diameter and totallyoverlap each other. The plates or disks are spaced less than a halfwavelength apart so only the TEM and TE modes can propagate where N isany whole number. The edge of the disks 19 and 21 are connected to eachother by a conductive band or rim 25 of conductive material to make theparallel plate lens feed assembly 11 a completely enclosed structureconfining the propagated energy therein. Near the periphery of theparallel disks l9 and 21 are coupled the 48 outer probes 27 which areequally spaced from each other and are arranged in a circular pattern.Each of these outer probes 27 are coaxial probes with the outerconductor 27a (as shown in FIG. 2) coupled to the top plate 19 and withthe inner conductor 27b being insulated from outer conductor 27a andextending in a coupling manner into the dielectric medium 23 locatedbetween plates 19 and 21 through a small aperture 19a in plate 19.

A second plurality of coaxial probes 29 (represented by dots in FIG. 1),sixteen 16) in number, for example, are arranged in an inner grouping orset near the center of the lens feed assembly 11. Each of the centralset of probes 29 have an outer conductor 29a and an inner conductor 29bwith the outer conductor 29a coupled to plate 21 and with the innerconductor 29b extending in a coupling manner into the dielectric medium23 through an aperture 21a in plate 21. The inner probes 29 are coupledto a power distribution network 31. This power distribution network 31in response to electromagnetic signal waves coupled to terminal 33, forexample, provides energy with selected relative power levels andselected relative phases to the 16 inner or central set of probes 29.These relative power levels and phases are selected to cause a resultantradiation pattern of a certain energy distribution to be emanatedtowards the outer probes 27 from the central grouping or set of probes29. This radiation pattern excites electromagnetic energy wave energy atthe peripheral probes 27 according to the certain energy distribution.In the example shown in FIG. 1, a directional radiation pattern,indicated by dashed line 39, is excited whereupon the peripheral probes27 are excited with the particular outer probe 34 receiving maximumpower and the outer probes 27 extending on either side of probe 34having symmetrically decreasing powers. The radiated pattern 39 is madesufficiently narrow, for example, so that the signal energy at thoseperipheral probes 27 beyond 45 on either side of probe 34 is considerednegligible.

As stated previously, the peripheral probes 27 are coupled by theseparate transmission lines 17 to the separate radiating elements '13located about the array structure 15. Since the signal energy at probe34 is maximum, maximum power is radiated out of the North-pointingradiating element 37 coupled thereto. Symmetrically decreasing power isradiated from the adjacent radiating elements 13 on either side ofelement 37. The resultant relatively narrow radiation pattern from thearray system 10 corresponds with that within the parallel platetransmission line assembly 11 with maximum strength of the beam pointingin the generally North-pointing direction of arrow 40. No appreciableradiation occurs beyond 45 on either side of the arrow 40. The resultingpattern distribution is similar to that of dashed lines 39.

The radiated beam from the elements 13 is commutated by adjusting therelative power level and phase of the signals at the inner probes 29 viaadjustments within the power distribution network 31. For example, if itis desired to radiate the relatively narrow beam with maximum strengthin the pointing EAST direction of arrow 40a, the power distribution ofenergy coupled to undivided probes of the central probes 29 and therelative phase of that energy at the undivided probes of the central setof probes 29 is selected at the power distribution network 31 so thatthe pattern within assembly 11 resemble pattern 47 (shown in dashedlines) in FIG. 1. In this arrangement, maximum radiation occurs at theparticular outer probe 41 of probes 27. Probe 41 is coupled via atransmission line 17 to the EAST pointing radiating element 43. Noappreciable radiation occurs, in the example, beyond about i45 on eitherside of element 43 and therefore maximum radiation occurs in generallythe EAST pointing direction. By adjusting the power ratio between thecentral probes 29 and the phase of the signals at the central probes 29,any selected direction of radiation within 7.5 (360/48) may be achieved.In order to collimate and/or to achieve a continuous scan or steering ofthe beam within finer increments, a controlled variable phase shifter 49is coupled in each of the leads 17 between the radiating elements 13 andthe probes 27.

Referring to FIG. 3, there is illustrated the manner in which the 48variable phase shifters 49 provide beam collimation and fine beamsteering within an arc of plus and minus 3.75. With the radiated patternas illustrated by dashed lines 39 in FIG. 1, the probe 34 of probes 27is excited with maximum power and with the power at the adjacent probesdescending in a symmetrical manner from either side of the probe 34.Maximum radiation under these conditions is in the general direction ofNorth-pointing direction arrow 40.

To the right of the particular outer probe 34 in FIG. 3 are the fourparticular adjacent outer probes 36a, 36b, 36c and 36d. To the left ofthe particular outer probe 34 are the four particular adjacent outerprobes 36e, 36f, 36g and 36h. Outer probe 34 is coupled via phaseshifter 49 and a particular one 18 of the transmission lines 17 toradiating element 37. Outer probe 36a is coupled via phase shifter 49aand transmission line 17a to radiating element 37a. Similarly, probe 36bis coupled to radiating element 37b via line 17b and phase shifter 4%.Probe 360 is coupled to radiating element 370 via line 17c and phaseshifter 49c. Probe 36d is coupled via line 17d and phase shifter 49d toradiating element 37d. To the left of North-pointing element 37 areantenna elements 37e, 37f, 37g and 37h. Probe 36e is coupled via linel7e and phase shifter 49e to radiating element 37e. Probe 36f is coupledvia line 17f and phase shifter 49f to radiating element 37f. Probe 37gis coupled via line 17g and phase shifter 49g to radiating element 373.Probe 36h is coupled via line 17h and phase shifter 49b to radiatingelement 37h.

When the phase shifters 49 and 49a through 49h are adjusted to centerthe beam in the centered direction of arrow 40 in FIG. 3, the wavefrontis along line 51. The phase shifter 49 and phase shifters 49a through49h are adjusted so that the wave from element 37 is delayed relative tothe waves from the adjacent radiating elements 49a through 49h and sothat the waves from the radiating elements 49a through 49h on eitherside of radiating element 37 are delayed in decreasing amounts fromelement to element to the right and left of the center element 37. Inother words, phase shifter 49 provides maximum delay, phase shifter 49aprovides less delay, phase shifter 49b provides less delay than phaseshifter 49a, phase shifter 490 provides less delay than phase shifter49b, and phase shifter 49d provides less delay than phase shifter 490.Phase shifters 49a and 49e provide equal delay, phase shifters 49b and49f provide equal delay, phase shifters 49c and 49g provide equal delay,and phase shifters 49a and 49h provide equal delay. The wavefront can beadjusted to be along dashed line 53 by adjusting phase shifters 49 and49a through 49h such that each of the phase shifters 49 and 49a through49h provide a relative delay to the corresponding waves that steadilyincreases to the right. The corresponding radiated beam thereby changesto the direction of arrow 55. This directional change may be in theabove example at +3.75. The main beam may be rotated 3.75 in thedirection of arrow 57 by reciprocally adjusting the position of thephase shifters 49 and 49a through 49h so that the relative delay to thecorresponding wave steadily increases to the left thereby providing awaveform along dashed line 59.

The power distribution network 31 and the spacing and arrangement of thecentral set of probes 29 can be made in accordance with the teachings ofC. O. Clasen, J. B. Rankin and O. M. Woodward, Jr. in an articleentitled, A Radial-Waveguide Antenna and Multiple Amplifier System forElectronic Scanning, RCA Review, September, l96l, pp. 543 thru 554.

A power distribution network with a central probe or monopole, a nextring or four probes, a next ring of eight probes, a next ring of 12probes and a final ring of 16 probes to achieve a single narrow beam ina desired direction is described in U.S. Pat. No. 3,090,956 of O. M.Woodward, Jr.

The above-described arrangements require many central probes, such as 16and 29 in the above examples, to achieve the required highly directionalpattern within the lens feed assembly. Also, the above arrangements mayhave difficulty in reducing side and back lobes to a sufficiently lowlevel.

FIG. 4 illustrates a 192-element array system 60 requiring a lessdirectional pattern within the parallel plate line lens feed assemblyand having no significant back lobes and fewer significant side lobes.Referring to FIG. 4, the array system 60 includes a radial parallelplate line, lens feed assembly 61, an outer circular array structure 63,192 radiating elements 65, transmission lines 66, 78 and 80, 48 phaseshifters 64 and 48 single pole four-way (SP4T) switches 67. For purposesof illustration, however, only 24-radiating elements 680 thru 68f, 69athru 69f, 70a thru 70f and 71a thru 71f of the I92 radiating elements 65are drawn. There are seven radiating elements 65 -represented by dotsand dashes between dots between each of the particular radiatingelements 65 drawn. Also, for purposes of illustration, only a few of thetransmission lines 66, 78 and 80, four-way switches 67 and phaseshifters 64 are illustrated, therebeing the number of phase shifters(48) and four-way switches (48) as indicated previously.

The parallel plate line lens feed assembly 61 is similar to the lensfeed assembly 11 in FIG. 1. Referring to FIGS. 5 and 6 illustrating aplan view and crosssectional view respectively of lens assembly 61, theassembly 61 includes a metal disk-shaped enclosure having a top wall 73and a bottom wall 95 with a rim 97 therebetween. There is a central setof nine probes 75j, 75a through 75h and an outer circle of 48 outerprobes 76. The assembly 61 differs from assembly 11 in that only nineprobes are used to make up the central set of probes with one of thenine probes being at the center of the lens feed assembly and thesurrounding set of eight probes being arranged in a single concentriccircle.

The lens feed assembly 61 can be provided by a circular disk-shaped body93 of 0.25 inch thick dielectric material covered with a copper disk toform top wall 73 on one surface and a copper disk on the oppositesurface to form bottom wall 95, a copper covering being provided aroundthe edge of the body to form the rim 97. The dielectric body can beZ-tron-G material manufactured by the Polymer Corporation, Reading, Pa.The disk-shaped body 93 has a radius of 10.47 inches. The 48 outerprobes 76 are arranged in a circle of a radius from the center of body93 of 9.01 inches. The outer conductor 103 of each of the probes 76 isfixed to the top disk 73 as shown in FIG. 6, and the inner conductors105 extend in an insulative manner through an aperture 104 in the topconductor disk 73 and through the dielectric body 93. The innerconductor 105 in this example extends all the way through the dielectricbody 93 to the opposite conductive disk 95 at the opposite surface. Inorder to match the central and outer probes to the line formed, a 50-ohmconical taper 105a of the center conductor canbe utilized as shown inFIG. 7. The forty-eight (48) outer probes 76 are equally spaced on the9.01 inch radius. The nine (9) central set of probes 75a, 75b, 75c, 75d,75e, 75f, 75g, 75h and 75j are located near the center with probe 75jlocated at the center of the radial parallel plate line lens feedassembly 61 and the other eight probes 75a, 75b, 75c, 75d, 75e, 75f, 75gand 75h arranged in a circle of a radius of 1.65 inches about the centerprobe 75j. A description of the placement of the central probes 75athrough 75h is achieved with the aid of placement lines 107 and 109 inFIG. 5. Placement line 107 is drawn through the center of assembly 61 soas to divide the lens feed assembly 61 in half with line 107 runningalong cross section 66 through the center of the assembly. Line 109 isdrawn to intersect line 107 at the center of the assembly 61 in FIG.with line 109 orthogonal to line 107. Probe 75a is located along aradius drawn at an angle of 0, to the left of line 107. Probe 75b islocated along a radius drawn at an angle of 6 to the right of line 107.Similarly, probe 75c is located along a radius drawn at an angle of 6 tothe left of line 107 and probe 75d is located along a radius drawn at anangle of 0, to the right of line 107. In this example 6 29.50. Probe 75eis located along a radius drawn at an angle of 0 above line 109. Probe75f is located along a radius drawn at an angle of 6 below line I09.Probe 75g is located along a radius drawn at an angle of 0 above line109. Probe 75h is located along a radius drawn at an angle of 0 belowline 109. In this example, 6 is equal to 29.50. Probes 75a thru 75h arelocatedabout 1.65 inches from center probe 75j.

Referring to FIG. 4, each of the 48 outer probes 76 is coupled to aseparate phase shifter 64 via transmission line 66. For purposes ofillustration in FIG. 4, only six probes (76a thru 76]) of the outerprobes 76 are shown connected to their appropriate phase shifters 64athru 64f via lines 66. Each of the four-way switches 67a thru 67f hasthe common terminal coupled to one of the outer probes 76a thru 76frespectively via lead 78 and four selectable terminals at the oppositeend coupled to four separate radiating elements via leads 80. These arefour times as many radiating elements 65 as there are outer probes 76(48 X 4 192). The four radiating elements 65 coupled to each four-wayswitch 67 are equally spaced about the total array structure 63. Forexample, four-way switch 67a in FIG. 4 is coupled at the one common endto probe 76a of the outer probes 76 via phase shifter 64a and is coupledat the opposite selectable terminal end at a first terminal 85 to theparticular North-pointing radiating element 68a. The second terminal 86of four-way switch 67a is coupled to the particular East-pointingradiating element 69a. The third terminal 87 of switch 67a is coupled tothe particular South-pointing radiating element a. The fourth terminal88 of switch 670 is coupled to the particular West-pointing radiatingelement 71a.

Coarse scanning of the antenna array system 60 is achieved by rotatingthe generated beam within the lens feed assembly 61 and by switching theposition of four-way switches 67 to couple the outer probes 76 to aselected one of the four radiating elements 65. The switching isaccomplished on an element-by-element basis as the beam is scanned aboutthe system by switching out the element furthest from the direction ofrotation and adding the next element in the direction of rotation viathe four-way switches 67 as the beam is scanned about the array.Although the operation described herein is beam scanning, it isunderstood that the switching can be done in any desired 'order toachieve a desired beam direction.

FIG. 8 is a sketch illustrating the switching technique. For convenienceof illustration, the array of radiating elements are placed in astraight line rather than curved. Also, for purposes of illustration,only the six outer probes 76a, 76b, 76c, 76d, 76e, and 76f of the 48outer probes 76 and six switches 67a, 67b, 67c, 67d, 67e and 67f of the48 four-way switches 67 are illustrated. As described above, the outerprobes 76 of the lens feed assembly 61 are coupled so that each outerprobe 76 (48 in number) is coupled to a four-way switch 67 (48 innumber) via a phase shifter 64. As mentioned previously, the four-wayswitch 67a coupler energy between outer probe 76a and radiating elements68a, 69a, 70a and 71a. Similarly, four-way switch 67b couples energybetween outer probe 76b and radiating elements 68b, 69b, 70b and 7 lb;four-way switch 670 couples energy between probe 760 and radiatingelements 68c, 69c, 70c and 710; four-way switch 67d couples energybetween probe 76d and radiating elements 68d, 69d, 70d and 71d; four-wayswitch 67e couples energy between probe 76c and radiating elements 68e,69e, 70e and 71a; and four-way switch 67f couples energy between probe76f and radiating elements 68f, 69f, 70f and 71f.

To achieve a beam directed to the northeast as indicated by arrow 73,for example, the switches 67a thru 67f are energized by a control source87 via leads 84 to switch all of the outputs from outer probes 76a thru76f to radiating elements 68a thru 68f via the leads 78 and 80 and phaseshifters 64. The central set of probes and 75a thru 7511 are energizedto produce a first cardioid pattern (shown by dashed line 81 in FIG. 8)with the maximum power divided between the outer probes 76c and 76d andlesser symmetrical powers to the outer probes 76b and 76e. Little or noappreciable power exists at the outer probes 76a and 76f. This resultsin an output power distribution indicated by dashed curve line 82 inFIG. 8 with the four-way switches 67a thru 67f in the position to couplethe power at probes 76a thru 76f to radiating elements 68a thru 68f.This produces a beam with maximum energy in the direction of arrow 73.Since the power to the other radiating elements 69a thru 69f, 70a thru70f and 71a thru 71f are completely switched out, no power is radiatedfrom these elements and therefore no side or back lobe signals emit fromthese other elements 65, greatly reducing the possibility of back orside lobes. Also, a greater percentage of the wave energy generated bycentral probe 75 is this system is utilized in achieving the desiredbeam than in the system of FIg.

In commutating the beam about the array 60, the FIG. switches 67a thru67f are sequentially switched element by element from the series ofradiating elements 68 to the series of radiating elements 69, from theseries of radiating elements 69 to the series of radiating elements 70,from the series of radiating elements 70 to the series of radiatingelements 71 and from the series of radiating elements 71 back to theseries of radiating elements 68. In scanning clockwise, the switches areenergized in the sequence 67a, 67b, 67c, 670', 67c, 67fand back to 67a.For example, to achieve scanning from the northeast radiated position,indicated by arrow 73, to the east position indicated by arrow 83, theradiated power distribution at the particular outer probes 76a thru 76fis altered with adjustment of the power and phase at inner probes 75 andthe selected position of the four-way switches 67a, 67b and 67c areswitched to couple power from the probes 76a, 76b and 760 to antennaradiating elements 69a, 69b and 69c. The central set of probes 75 havetheir power distribution altered as indicated by pattern 810 so that themaximum power is centered at outer probe 76a with equal power at theprobes 76b and 76f. A negligible low power level exists at probes 76cand 76c and a minimum power level exists at probe 76d. The result is apower distribution as indicated by curved dashed line 83 and a radiatedbeam with the main lobe pointing in the East direction of arrow 85.Coarse beam scanning is thereby done as discussed previously byswitching on" sequentially the antenna elements 70a, 70b, 70c, 70d, 70cand 70fwhile switching off sequentially elements 69a, 69b, 69c 69f. Acomplete 360 scan is achieved by switching on" elements 71a, 71b, 71c71f while switching of 70a, 70b, 70c 70f and then switching on" 68a,68b, 68c 68fwhile switching off" elements 71a, 71b, 71c 71f. While thisswitching is being done, the cardioid pattern is being rotated withinthe lens feed assembly 61.

The fine steering to provide collimation and a continuous scan isachieved by the phase shifters 64 located between each four-way switch67 and the outer probes 76. Control signals to the phase shifter 64 andswitches 67 are provided by a control signal from source 87 via leads84a.

The desired rotatable cardioid-like pattern as illustrated and discussedin connection with FIG. 8 is provided by generating two rotating phaseomnidirectional patterns of reciprocal phase rotation represented bypatterns 106 and 108 in FIG. 9 and by combining these with a uniformphase omnidirectional pattern as represented by pattern 113 in FIG. 9.The phase at the one rotating phase omnidirectional pattern 106, forexample, goes clockwise from to 90, 90 to 180, 180 to 270 and 270 to 360as shown in FIG. 9. The phase at the other rotating omnidirectionalpattern 108, for example, goes clockwise from 0 to 270, 270 to 180, l80to 90 and 90 to 0 as shown in FIG. 9. Combining these two counterrotational phase patterns results in a figure-eight pattern. Byadjusting the phase between the two counter rotating omnidirectionalpatterns so that one is given a positive (b and the Otherjgiven an equalnegative d), the orientation of the figureeight pattern can beselectably positioned in any given direction. For example, by adding a+30 to one rotating omnidirectional pattern to achieve the phaserotation shown in FIG. 10, the other rotating omnidirectional patternshould have a or 30 to achieve the other rotating phase omnidirectionalpattern as shown in FIG. 11. In this case the orientation of thefigureeight pattern is rotated approximately 30. Each of these twocounter rotating phase omnidirectional patterns is generated by twofigure-eight patterns of equal power and at phase quadrature.

FIG. 12 illustrates the feed system 117 for properly exciting the innerprobes to produce the selected cardioid type energy distribution withinthe parallel plate line lens feed assembly 61 and to commutate thesedistributions within the assembly 61 by means of phase settings to thephase shifters.

The center probe 75j in FIGS. 5 and 12 excites a uniform phaseomnidirectional radial pattern within the radial parallel platetransmission line lens feed assembly 61. Each of probes 75a and 75b areexcited at a given phase and probes 75c and 75d are excited with equalpower as probes 75a and 75b but at a 180 phase difference to produce thefirst figure-eight pattern as illustrated by line in FIG. 13. The probes75e and 75f are excited with equal power and in phase. The phase of thesignals at probes 75e and 75f are at phase quadrature with the phase ofthe signals at probes 75a and 75b Probes 75g and 75h are excited withequal power as probes 75e 75f but at a 180 phase difference to providethe second figure-eight pattern in phase quadrature as illustrated byline 111 in FIG. 13.

Referring to FIG. 12, the probes 75a and 75b are coupled to arms 120aand 12% of hybrid 120. The hybrids herein may be, for example, rat racehybrids. The summing lead 1200 of hybrid 120 is coupled to hybrid at arm125a. The difference lead 120d of hybrid 120 is open circuited at theend. Similarly, probes 75c and 750' are coupled respectively to arms121a and l21b of hybrid 121. The summing arm 121c of hybrid 121 iscoupled to hybrid 125 at arm 125b. The difference lead 121d of hybrid121 is open circuited at the end. The summing arm 125a of hybrid 125 isterminated in an open circuit, and the difference arm 125d is coupled topoint 126. Signals coupled at point 126 are divided equally at hybrid125 with the signals applied to hybrid 120 being out of phase withrespect to those at hybrid 121. This phase and power relationshipprovides for the first figure-eight pattern 110 in FIG. 13.

Similarly, probes 75e and 75f are coupled to arms 127a and 127brespectively of hybrid 127. The summing arm 127c of hybrid 127 iscoupled to arm 131a of hybrid 131. The difference arm 127d is terminatedin an open circuit. The probes 75g and 75h are coupled to arms 129a and12% respectively of hybrid 129. The summing arm 129c of hybrid 129 iscoupled to arm l31b of hybrid 131. The difference arm 129d is terminatedin an open circuit. The summing arm 1310 is terminated in an opencircuit and the difference arm 131d is coupled to point 128. A signal atpoint 128 is coupled equally to hybrids 127 and 129 with the signalscoupled to hybrid 127 being 180 out of phase with respect to signalscoupled to hybrid 129. This phase and power :relationship provides forthe second figure-eight pattern.

The two rotating omnidirectional patterns 106 and 108 in FIG. 9 withopposite phase rotation is provided by coupling the 3 db 90 (quadrature)coupler 140 between the points 126 and 128 at one end and the points 141and 143 at the opposite end. One half the signal at point 141 is coupledto point 126 and the other half of the signal is phase shifted 90 topoint 128. Similarly, half of the signal at point 143 is coupled topoint 128 and the other half of the signal is coupled to point 126 with90 phase shift. In the case of reciprocal operation signals at eitherpoints 126 or 128 are equally divided and coupled 90 out of phase topoints 141 and 143.

By adjusting the relative phase shift of the two rotatingomnidirectional patterns, as mentioned previously, the adjustabledirection figure-eight pattern is provided. This adjustment of relativephase shift is accomplished by phase shifters 145 and 147 locatedbetween hybrid 149 and points 141 and 143. The phase adjustment of phaseshifters 145 and 147 is made so that phase shifter 145 be made toprovide a negative 4) phase shift, for example 30, when phase shifter147 provides a positive d: or in the example +30. The result is the twocounter rotating phase omnidirectional patterns in FIGS. and 11 and aresultant figure-eight pattern. The summing arm 149c of hybrid 149 iscoupled to port 151 of directional coupler 150. The difference arm 149dis coupled to difference port 157. The signal information at thisdifference arm 149d is that from a figure'eight pattern orthogonallyoriented to the selected figure-eight pattern as illustrated by pattern118 in FIG. 9. To achieve the desired cardioid shape, the uniform phaseomnidirectional pattern (represented by pattern 113 in FIG. 9) is addedto the selectable figure-eight pattern. The power ratio of the uniformphase omnidirectional pattern 113 relative to the figure-eight patternis in the order of 3 to I. This can be achieved by a 6 db directionalcoupler 150 whereby 75 percent of the power at sum terminal 155 isapplied to terminal 153 of coupler 150 and 25 percent of this power isapplied to sum port 1490 of hybrid 149. The result is a selectedcardioid pattern illustrated by pattern 119 in FIG. 9. At the differencearm 149d of hybrid 149 is provided the results of a figure-eight patternillustrated by pattern 118 with the null pointing in the direction ofthe maximum signal strength of the selected cardioid-like pattern 119 asshown in FIG. 9.

It is understood that the well known reciprocal theory of antennasapplies and whatever performs for generating a radiated pattern performsin the reverse when a radiated pattern is received.

A difficulty may be encountered due to cross coupling between the innerprobes 75. Isolation between points 126 and 128 and point 130 alongcenter probe 75j is had by adjusting the lengths of the difference armstubs 120d, 121d, 127d and 129d in hybrids 120, 121, 127 and 129 and thesumming arm stubs 1250 and 1310 in hybrids 125 and 131. The adjustmentof the length of these stubs is done empirically by varying the stublengths until minimum cross coupling occurs.

The above-described parallel plate line lens feed assembly 61 includingthe feed distribution network 117 in FIG. 12 was built and tested over afrequency range of 1,250 1,325 MHz. With equal to 0 (zero degrees 6phase shift) at phase shifter 145 and 147 the peak of the sumdistribution (maximum field strength) of the cardioid-like pattern wasaligned with the sixth probe 76 to the right of outer probe 760. Alsothe null of the difference distribution was aligned with this same sixthprobe to the right of probe 76a. When 80 is applied to phase shifter 147and 80 is applied to phase shifter 145, the pointing direction changedwith the peak of the cardioid-like pattern (maximum field strength)pointing between the sixteenth and seventeenth probe to the right ofprobe 76a. The amplitude and phase levels did not change as thedistribution was commutated.

In optimizing the system, the central set of probes 75a thru 75h arearranged with a degree of arc (20 for example) between the probes of apair being between 50 and Further in optimizing the system the radius ordistance from the center probe j to one of the other central set ofprobes 75a thru 75h is between 0.2 to 0.4 wavelengths in the dielectricmedium of the assembly 61.

In accordance with another embodiment shown in FIG. 14 of the presentinvention, the assembly 161 includes a central set of five probes 175.The five probes are arranged as shown in FIG. 14 with a central probeThe paired probes in FIG. -5 are replaced by single probes 175a thru175d placed on a line bisecting the arc of the replaced probes 75 inFIG. 5 and located considerably closer to the center probe 175j.

What is claimed is:

l. A ring-like antenna array system comprising:

a pair of parallel overlapping conductive plates spaced from each otherwith a dielectric medium therebetween to form a transmission line,

a first plurality of probes being arranged in a ring-like pattern nearthe periphery of the parallel overlapping conductive plates, each ofsaid first plurality of probes having a portion hereof extending intothe field region of said transmission line,

means including a second plurality of probes being grouped in a patternnear the center of said parallel conductive plates for generating aradiated pattern of electromagnetic energy with a selected amplitudedistribution of that energy within said transmission line to therebyexcite a given group of said first plurality of probes,

a plurality of radiating elements arranged in a ringlike pattern, thenumber of said radiating elements being N times as many elements asthere are probes in the first plurality of probes, where N is an integergreater than one,

a plurality of N-way switches, said switches being equal in number tosaid first plurality of probes,

each of said N-way switches being electrically coupled to a differentone of said first plurality of probes, N number of said radiatingelements being selectively coupledto each N-way switch, said N radiatingelements coupled to each switch being equally spaced about the array,

and means for changing the selected switch positions of said N-wayswitches to determine the radiating elements electrically coupled toeach of said first plurality of probes and thereby control with thegenerating means the direction of the beam radiated from the system.

2. The combination of claim 1 including collimating means coupledbetween said first plurality of probes and said N-way switches.

3. The combination in claim 2 where N is four.

4. The combination in claim 2 wherein said collimating means includes avariable phase shifter coupled between each N-way switch and one of saidfirst plurality of probes.

5. The combination in claim 1 wherein said means for generating aradiated pattern within said transmission line includes a powerdistribution network so arranged as to produce a rotatable cardioid-likepattern and a difference mode pattern within the region bounded by theplates.

6. The combination in claim 5 wherein said means for generating saidrotatable cardioid-like pattern further includes a pair of phaseshifters and a coupler, a first of said phase shifters being arranged toprovide a phase shift equal in phase shift but of opposite sign to thatprovided by the second of said phase shifters.

7. The combination in claim 6 wherein said coupler is arranged tocombine the power of a fixed omnidirectional pattern and the resultantpower from said two counter rotating omnidirectional patterns.

8. The combination in claim 1 wherein said second plurality of probes isfive probes with one central probe and four probes arranged in a circlecoaxially with the central probe.

9. The combination in claim 1 wherein said second plurality of probes isnine with one center probe and eight probes arranged in a circlecoaxially with the center probe.

10. The combination in claim 9 wherein said eight coaxially arrangedsecond plurality of probes are distributed in pairs such that each pairis of are from the next adjacent pair of probes.

1. A ring-like antenna array system comprising: a pair of paralleloverlapping conductive plates spaced from each other with a dielectricmedium therebetween to form a transmission line, a first plurality ofprobes being arranged in a ring-like pattern near the periphery of theparallel overlapping conductive plates, each of said first plurality ofprobes having a portion hereof extending into the field region of saidtransmission line, means including a second plurality of probes beinggrouped in a pattern near the center of said parallel conductive platesfor generating a radiated pattern of electromagnetic energy with aselected amplitude distribution of that energy within said transmissionline to thereby excite a given group of said first plurality of probes,a plurality of radiating elements arranged in a ring-like pattern, thenumber of said radiating elements being N times as many elements asthere are probes in the first plurality of probes, where N is an integergreater than one, a plurality of N-way switches, said switches beingequal in number to said first plurality of probes, each of said N-wayswitches being electrically coupled to a different one of said firstplurality of probes, N number of said radiating elements beingselectively coupled to each N-way switch, said N radiating elementscoupled to each switch being equally spaced about the array, and meansfor changing the selected switch positions of said Nway switches todetermine the radiating elements electrically coupled to each of saidfirst plurality of probes and thereby control with the generating meansthe direction of the beam radiated from the system.
 2. The combinationof claim 1 including collimating means coupled between said firstplurality of probes and said N-way switches.
 3. The combination in claim2 where N is four.
 4. The combination in claim 2 wherein saidcollimating means includes a variable phase shifter coupled between eachN-way switch and one of said first plurality of probes.
 5. Thecombination in claim 1 wherein said means for generating a radiatedpattern within said transmission line includes a power distributionnetwork so arranged as to produce a rotatable cardioid-like pattern anda difference mode pattern within the region bounded by the plates. 6.The combination in claim 5 wherein said means for generating saidrotatable cardioid-like pattern further includes a pair of phaseshifters and a coupler, a first of said phase shifters being arranged toprovide a phase shift equal in phase shift but of opposite sign to thatprovided by the second of said phase shifters.
 7. The combination inclaim 6 wherein said coupler is arranged to combine the power of a fixedomnidirectional pattern and the resultant power from said two counterrotating omnidirectional patterns.
 8. The combination in claim 1 whereinsaid second plurality of probes is five probes with one central probeand four probes arranged in a circle coaxially with the central probe.9. The combination in claim 1 wherein said second plurality of probes isnine with one center probe and eight probes arranged in a circlecoaxially with the center probe.
 10. The combination in claim 9 whereinsaid eight coaxially arranged second plurality of probes are distributedin pairS such that each pair is 90* of arc from the next adjacent pairof probes.